Ultra wideband (uwb) baby monitors for detection of infant cardiopulmonary distress

ABSTRACT

Ultra wideband patient monitoring systems, and particularly baby monitoring systems, adapted to prevent reflective loss between the antenna and the patient&#39;s body. The devices, systems and methods described herein may be used to efficiently couple UWB energy to a patient for patient monitoring. In particular, described herein are impedance transformer pads, mats and the like, upon which a patient may comfortably lie while being monitored via one or more UWB sensors (e.g., antenna); the impedance transformer pads help match the impedance and prevent reflective loss of UWB energy. Also described herein are bassinets, including NICU bassinets and baby monitors.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 13/196,139, filed Aug. 2, 2011, titled “Ultra Wideband (UWB)Baby Monitors For Detection Of Infant Cardiopulmonary Distress,”Publication No. US-2012-0059268-A1, which claims priority to U.S.Provisional Patent Application No. 61/369,843, titled “Non-Contact BabyMonitor for the Neonatal Intensive Care Unit With Application to HomeMonitoring for Detection of Cardiopulmonary Distress” filed on Aug. 2,2010, each of which is herein incorporated by reference in its entirety.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference in their entirety to the sameextent as if each individual publication or patent application wasspecifically and individually indicated to be incorporated by reference.

FIELD

Described herein are non-contact baby monitors for monitoring an infant.In particular, described herein are ultra wideband (UWB) baby monitoringsystems for measuring an infant's cardiopulmonary state, and detectingdistress. Included herein are devices including integrated UWB monitorsand bassinettes and/or impedance transformer pads for optimizing thetransfer of energy between the UWB system and the infant beingmonitored.

BACKGROUND

The Neonatal Intensive Care Unit (NICU) is a unit of a hospitalspecializing in the care of ill or premature newborn infants.Approximately 500,000 babies born in the United States each year aretreated in a neonatal intensive care unit with the most common causesfor admission being premature birth, difficult delivery, breathingproblems, infections, and birth defects.

NICU protocols specify continuous monitoring of vital signs, to alertcaregivers of a deteriorating condition or an emergent event. Theseevents can develop slowly, as in hyperkalemia, which can lead to cardiacarrhythmia, or can appear suddenly, as commonly seen in respiratorydistress. Current monitoring techniques rely heavily on ECG technologywhich requires direct skin contact via adhesive electrodes and are thushighly undesirable due to the need for skin contact. Premature babieshave extremely delicate skin that is susceptible to damage andinfection, increasing their risk of complications and potentiallyextending their time in the NICU. Premature babies younger than 30 to 32weeks have thin skin, lacking the layers of body fat that would havebeen put on during the final weeks of pregnancy. In extremely prematurebabies, the coarse, top layer of skin hasn't yet formed. During theirstay in the NICU, every attempt is made to minimize skin contact, evenlimiting physical contact by parents and caregivers.

Besides the potential for complications resulting from direct placementof electrodes on the infant's skin, there is an identified need toreduce the amount of physical contact to the neonatal intensive carepatient since contact is known to stress the infant and can compromiserecovery and development. Thus, monitoring technologies that minimizeplacement of electrodes on the patient as well as minimize the need forcaregivers to touch the patient to collect vital signs information arehighly desirable.

Thus, there is a need for non-contact baby/infant monitors, and thisneed is particularly acute in the NICU context. A number of variationsof non-contact UWB sensors have been proposed, such as those offered bySensiotec, and described in U.S. Pat. No. 7,432,847 and U.S.2009/0227882. However, these devices suffer from limitations inherent intheir configuration resulting in a loss of signal strength. This loss ofsignal strength results in less efficient devices, and may limit thepenetration and accuracy. Thus, it would be useful to provide systems,devices and methods for monitoring an infant, and particularly an infantin an NICU setting in a reliable, low-energy and non-contact fashion.Described herein are systems, devices and methods that may address thisneed.

SUMMARY OF THE DISCLOSURE

Described herein are non-contact monitoring UWB systems, which may alsobe referred to as UWB radar systems or UWB radar monitoring systems. Inparticular, described herein are UWB monitoring systems that provideimpedance matching between the emitter (and/or receiver) antenna and thepatient such that the emitted UWB energy is efficiently transmitted andreceived. In some variations the system may include an impedancetransformer, configured as a pad or other reclining surface that matchesthe impedance (e.g., dielectric) of the antenna to that of the patient.The impedance transformer may thereby reduce the reflection of UWBenergy between the antenna and the patient, preventing energy loss andallowing more efficient operation. In some variations, the systemincludes a dedicated bassinet in which the UWB components have beenintegrated; integration may allow optimization of the positioning of theUWB antenna. Also described herein are systems configured to be usedwith existing cribs or basinets for monitoring (including at-homemonitoring).

For example, described herein are impedance transformer pads for usewith an ultra wideband (UWB) monitoring system to minimize reflectiveloss of the UWB energy. The impedance transformer pads may include: asoft or resilient recumbent surface formed at least in part from animpedance transformer region having a thickness of between about 0.4 cmand 7 cm, wherein the impedance transformer region has at least onelayer having a dielectric constant of between about 5 and about 20; anda UWB antenna abutting the impedance transformer region; wherein the UWBantenna is configured to transmit and receive UWB signals through theimpedance transformer region to monitor the patient resting on the pad.

Any of the 1, wherein the pads described herein may be for use with (orintegrated into) a bassinet. For example, the recumbent surface may besized to fit into a bassinet.

In some variations the impedance transformer region has a singlehomogenous layer. This layer may have a dielectric value that isintermediate between the dielectric constant of the UWB antenna(s) andthe patient (e.g., the geometric mean). Impedance transformer regionsmay include multiple layers (e.g., 2, 3, 4, 5, 6, etc.); virtually anynumber of layers may be included, however, this may increase the costand complexity of the devices. In some variations, the impedancetransformer region has at least two adjacent planar layers, wherein eachplanar layer has a different thickness and dielectric constant. Forexample, in some variations, the impedance transformer region has threeadjacent planar layers, wherein each planar layer has a differentthickness and dielectric constant.

The impedance transformer region (including each layer thereof) may beformed of any appropriate material that may take the desired thicknessand dielectric properties, as well as being biocompatible, pliable/soft,easy to clean, non-toxic, hypoallergenic, and water proof. For examplein some variations the layer(s) of the impedance transformer region areformed of silicone.

The size of the impedance transformer region may have a thickness ofbetween about 0.5 cm and 5 cm, including all of the layers, if more thanone layer is present.

In some variation, the pad includes a backing layer beneath theimpedance transformer region and the UWB antenna. The pad may include aplurality of UWB antennas beneath and abutting the impedance transformerregion. The antenna may be configured to emit a UWB signal having abandwidth, and wherein the impedance transformer region has one or moreplanar layers each having a dielectric and wherein and the thickness ofeach layer is approximately one quarter or one half of the wavelength ofthe center frequency of the bandwidth in the dielectric of that layer.

Also described herein are ultra wideband (UWB) patient monitoringsystems having an impedance transformer pad to minimize reflective loss,the system having a UWB bandwidth for emitting sensing signals, thesystem further comprising: an impedance transformer pad having a UWBantenna beneath an impedance transformer region, the antenna configuredto transmit UWB signals through the impedance transformer region to apatient resting on the pad, wherein the impedance transformer region hasone or more planar layers and the thickness of each layer isapproximately one quarter or one half of the wavelength of the centerfrequency of the bandwidth in the dielectric of that layer; and aprocessor configured to receive signals from the UWB antenna to monitorthe patient. Any of the systems and devices described herein may alsoinclude UWB electronics (which may be separate from or incorporated intoa processor) for generating a UWB signal for transmission and receptionby the UWB antenna. Such UWB electronics may include signal generators,D/A and A/D converters, timing circuitry, comparators, amplifiers,filters, and the like. For example see U.S. Pat. No. 7,725,150, U.S.patent application Ser. No. 12/765,680, published as US 2010/0274145A1,and U.S. patent application Ser. No. 12/749,861, published as US2011/0060215A1. The UWB electronics are typically configured to generatethe UWB signal(s) for emitting from the antenna(s) and processing thereceived signal (reflections) to extract physiological data.

As mentioned, the impedance transformer pad may also include a backinglayer behind the impedance transformer layer and the antenna. Thebacking layer may support the recumbent surface formed by the impedancetransfer region (or it may form the recumbent surface with the impedancetransfer region).

In some variations the pad includes a cable connecting the antenna ofthe impedance transformer pad to the UWB electronics and/or processor.

In general, the impedance transformer pad is flexible, hypoallergenic,and water proof. The pad may be used with a crib or bassinet. Forexample, the pad may be sized for use in a crib or bassinet, including aNICU. In some variation the pad includes indicators (e.g., markings)indicating the location of the sensors/antenna and/or the preferredpositioning for the patient (e.g., infant) lying upon the pad.

In some variations the impedance transformer region of the impedancetransformer pad has a single homogenous layer configured as a quarterwavelength layer, wherein the thickness is approximately one quarter ofthe wavelength of the center frequency of the bandwidth in thedielectric of the layer. In some variations the impedance transformerregion of the impedance transformer pad has two or more layers.

In some variations, the impedance transformer region of the impedancetransformer pad has three layers, comprising adjacent planar layersconfigured as a quarter wavelength layer, a half wavelength layer, and aquarter wavelength layer.

In any of the variations described herein, the impedance transformer padmay include a plurality of UWB antennas. Different antenna may be used,or the same types of antenna. For example, the UWB antenna may be an airantenna (e.g., an antenna readily commercially available that isconfigured for transmission in air, and therefore is designed totransfer energy into a medium with a relative dielectric constant ofapproximately 1).

Also described herein are methods of monitoring an infant using an ultrawideband (UWB) radar system including an impedance transformer pad, themethod comprising: placing the infant atop the impedance transformerpad; and emitting a UWB signal from a UWB antenna, wherein the signalpasses from the antenna, through an impedance transformer region of theimpedance transformer pad and into the infant, further wherein theimpedance transformer region has at least one layer having a dielectricconstant of between about 5 and about 20, wherein the impedancetransformer pad reduces the impedance miss-match between the antenna andthe infant to reduce reflective loss of energy from the signal.

The method may also include receiving a reflected UWB signal from theinfant using the UWB antenna, and analyzing the signal to monitor theinfant. The method may include determining a vital sign for the infantand in some variations, displaying the vital sign. For example, thesignal may be analyzed to determine heart rate, etc. The system mayinclude one or more alarms for indicating when the infant is undergoingdistress based on the monitoring. In general, the systems, methods anddevices described herein may use one or more antennas that can beconfigured as emitter antenna (transmitting the UWB signal) and/orreceiver antenna (receiving the UWB signal reflected), or both. Thus, arecovering antenna can be the same as the transmitting antenna.

The step of emitting the UWB signal may include passing the signalthrough the impedance transformer region wherein the impedancetransformer region has a single homogenous planar layer having adielectric that is the geometric mean of the dielectric of the antennaand the dielectric of the infant. In some variations, emitting the UWBsignal comprises passing the signal through the impedance transformerregion wherein the impedance transformer region has a thickness betweenabout 0.4 cm and about 7 cm.

The step of emitting the UWB signal may include passing the signalthrough the impedance transformer region wherein the impedancetransformer region has a plurality of layers each with a dielectricvalue, wherein the thickness of each layer is approximately one quarteror one half of the wavelength of a center frequency of the bandwidth ofthe emitted signal in the dielectric of that layer. In general the stepof emitting comprises emitting the UWB signal from the antenna to theinfant through the impedance transformer region without the UWB passingthought the air or a standard mattress (which may result in increasedloss when the impedance transfer pads described herein).

In any of the method described herein, placing the infant on the pad maycomprise placing the infant atop the impedance transformer pad within anNICU bassinet.

Also described herein are ultra wideband (UWB) baby monitoring systemsincluding: an impedance transformer pad having a soft or resilientrecumbent surface upon which a baby may rest; a UWB antenna coupled tothe impedance transformer pad and configured to emit a UWB signalthrough the transformer pad and into the baby, wherein the impedancetransformer pad is configured to prevent reflective loss of more than50% of energy of the UWB signal; and a processor in communication withthe UWB antenna and configured to monitor the baby when the baby isresting on the impedance transformer pad. As mentioned, any of thesystems and devices described herein may also include UWB electronics aspart of (or in addition to) the processor.

The system may generally be configured to apply UWB signals in abandwidth having a center frequency, wherein the impedance transformerpad comprises an impedance transformer region forming the recumbentsurface, the impedance transformer region having one or more planarlayers each with a different dielectric value. For example, the systemmay be configured to apply UWB signals in a bandwidth having a centerfrequency, wherein the impedance transformer pad comprises an impedancetransformer region forming the recumbent surface, the impedancetransformer region having one or more planar layers each with adielectric value, wherein the thickness of each layer is less than orequal to one half of the wavelength of the center frequency in thedielectric of that layer. Specifically, the system may be configured toapply UWB signals in a bandwidth having a center frequency, wherein theimpedance transformer pad comprises an impedance transformer regionforming the recumbent surface, the impedance transformer region havingone or more planar layers each with a dielectric value, wherein thethickness of each layer is approximately one quarter or one half of thewavelength of the center frequency in the dielectric of that layer.

As mentioned above, the impedance transformer pad may be configured tofit within a bassinet. Further, the impedance transformer pad may bemade of a non-toxic, hypoallergenic, and water proof material.

Also described herein are bassinets configured for ultra wideband (UWB)monitoring of an infant. For example, the bassinet may include: atemperature-regulated bassinet enclosure having walls and a lowersurface; and at least one UWB antenna integrated into the bassinet andconfigured to emit UWB energy into an infant within the bassinet fromthe lower surface of the bassinet; wherein the lower surface of thebassinet impedance matches to minimize reflective loss of UWB energybetween the UWB antenna and the infant.

In some variations, the lower surface of the bassinet comprises animpedance transformer pad covering the UWB antenna so that the UWBantenna emits UWB signals through the impedance transformer pad. Any ofthe pads described above may be used; in some variations the pad isintegrated into the bassinet.

The UWB antenna may be configured to apply UWB signals in a bandwidthhaving a center frequency, further wherein the lower surface comprisesan impedance transformer region covering the UWB antenna, on which aninfant may rest, wherein the impedance transformer region has one ormore planar layers each with a dielectric value, wherein the thicknessof each layer is less than one half of the wavelength of the centerfrequency in the dielectric of that layer.

In some variations, the UWB antenna may have a dielectric approximatelymatched to the dielectric of the infant. For example, the antenna may beconfigured to have an dielectric of approximately 50. The outer surfaceof the dielectric may be adapted so that it is comfortably for theinfant to rest on top of. For example, the upper surface of the antennamay be soft, compliant, etc. In any of the variation described herein,the bassinet may include a plurality of UWB antennas. Further, thebassinet may include a processor (e.g., a UWB radar processor)configured to receive signals from the UWB antenna to monitor theinfant, and/or UWB electronics for emitting and receiving UWB signalsand extracting physiological data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one variation of an NICU bassinet with one variation of aUWB monitoring system.

FIG. 2 shows one variation of a UWB monitoring system for an infant,including an impedance matching pad.

FIG. 3A is a partial sectional view through one variation of animpedance transformer pad. FIG. 3B shows a top view of the impedancetransformer pad of FIG. 3A.

FIG. 4A is a partial sectional view through another variation of animpedance transformer pad. FIG. 4B is a top view of the impedancetransformer pad of FIG. 4A.

FIG. 5 shows another variation of a UWB monitoring system for an infant,including an impedance matching pad having three layers in the impedancematching region.

DETAILED DESCRIPTION

The Ultra-Wideband (UWB) monitoring systems described herein may also bereferred to as medical radar systems. These systems allow for miniature,extremely low-power medical monitoring systems that are safe andeffective. UWB medical radar is an active imaging technology similar infunctional concept to ultrasound but is based on electromagnetic, ratherthan sonic energy. In practice, the systems described herein emit amicro-pulse of electromagnetic energy, typically on the order of onehundred picoseconds in duration, which propagates into the human body.As the energy enters the body, small amounts of the incident energy arereflected back to the device. The reflections are primarily a result ofthe differences in dielectric properties of the underlying tissues andorgans, and can be detected as signals (“reflection signal energy”). Thereflection signal energy is then received and processed using signalprocessing algorithms to extract information on the location, size, andrelative movement of the illuminated tissues and organs. The short pulseduration also allows the radar to ‘see’ at much closer distances andwith finer resolution than more traditional radar systems. The energytransmitted to the patient is typically reduced by unwanted reflectionsarising between the UWB antenna and the patient's body (“reflectionloss”). The one-way reflection loss in some prior art UWB systems may beas great as 85-90% of the emitted energy. This loss results in lowersignal strength overall, and a significant decrease in the reflectedenergy from the internal anatomical structures, making extraction of thedesired physiological data more difficult and less accurate andreliable.

Thus, the systems described herein describe systems for reducing thereflection loss of the UWB sensor system. All of the UWB systemsdescribed herein employ extremely low power electromagnetic energycapable of passing through materials such as plastics, clothing, air andbone without needing direct skin contact, conductive gels, electrodes orleads. The actual transmitted power levels are well below thresholds setfor governmental safety standards, as well as below those used bywidely-adopted commercial wireless technology (e.g. cell phones,Bluetooth devices, ZigBee devices, 2.4/5.8 GHz cordless phone, wirelessintercoms and baby monitors, and 802.11 wireless internet equipment).

The infant in the NICU environment provides some unique challenges andopportunities for non-invasive vital signs monitoring. First, the NICUinfant is typically a premature baby and, thus the anatomical structuresare very small, complicating the ability to collect vital signs datausing non-contact active techniques. Second, a baby admitted to a NICUstays in a specialized isolation bassinette which provides a protectiveenvironment for the infant. The bassinette is typically an enclosedstructure, controlling temperature, light, humidity, and air flow. Theyfeature transparent sides that are typically made from clear plastic.The tops are removable—either manually or motorized, and often includesa switch that is used to signal when the top is open or closed.

In some variations of the devices described herein, the system includesa UWB medical radar to interrogate the volume of the isolationbassinette, allowing non-contact monitoring of vital signs includingcardiac and respiratory activity, without touching the infant. Thesebassinettes are typically made using transparent plastic enclosure and amattress pad—both of which are non-conductive; UWB radar can operatethrough the walls or the pad.

UWB Sensor Attached to Bassinet

In some variations, the systems described herein include bassinets withintegrated UWB monitoring systems. In this variations, the UWBmonitoring system and bassinet may be configured together to optimizethe signal transmission and detection and therefore the efficiency ofthe monitoring system. For example, the UWB antenna(s) may be arranged(and may be fixed in positions) around the bassinet in a manner thatoptimizes the detection of infant vital signs. In some variations thebassinet may include one or more indicators for positioning the infantwithin the bassinet in a manner that provides optimal monitoring. Inaddition, the bottom of the bassinet may include a recumbent surfacethat is configured to optimize the transmission of UWB energy forsensing an infant. The UWB system may also be configured to sense thepresence/absence of an infant in the bassinet, and to automaticallymonitor or turn off monitoring, and to emit or provide various alertsbased on the condition of the infant.

For example, FIG. 1 shows one variation of a bassinette enclosure 101 inwhich one or more radar components (e.g., transmitter 103, receiver 105,or transceiver) on the walls of the isolation bassinette allow off-bodydetection and monitoring of cardiac and respiratory activity. In FIG. 1,the NICU bassinet includes a UWB sensor configured in a bistatic mode,with transmission 103 at one end and reception 105 at the other end ofthe enclosure 101). Thus, in general, the system architecture couldinclude monostatic, bistatic, or multistatic topologies with locationsincluding bassinette corners, sides, top, bottom, front or rearsurfaces. In one implementation, the components would be secured to theexterior surfaces to minimize the potential of any physical interactionwith the infant. However, in some variations it may be advantageous tomount the radar components inside the bassinette—e.g. one or morecorners, to provide a wider search area. The integrated cover switch canbe used to disable the radar when the top cover is open.

In some variations, the system includes a plurality of UWBtransmitter/receivers positioned in predetermined locations within thebassinet. The transmitter, receiver or transceiver may be arranged in avariety of configurations. In one variation, the UWB components arelocated in an interior corner (e.g., co-located transmitter and receiveroperated in monostatic mode). Alternatively the UWB components may belocated in any two opposite interior corners with separate transmitterand receiver operated in bistatic mode. In some variations, the UWBcomponents are located on the exterior short side of the bassinet with aco-located transmitter and receiver operated in monostatic mode. In somevariations the UWB components are located in opposite exterior shortsides with separate transmitters and receivers operated in bistaticmode. In some variations, UWB components are located on an exterior longside with co-located transmitter and receiver operated in monostaticmode. Alternatively, the UWB components may be located on oppositeexterior long sides with separate transmitters and receivers operated inbistatic mode. In some variations the UWB components may be operated onadjacent exterior long sides with separate transmitters and receiversoperated in bistatic mode. In general, combination of three or moreadjacent exterior long sides with separate transmitter and receiver maybe operated in multistatic mode.

In addition to the variations just described, the bassinet may beconfigured so that UWB components (e.g., transmitter, receiver, ortransceiver) form part of or are coupled to a recumbent surface (such asthe bottom of the bassinet or a pad for the bottom of the bassinet)which may be impedance matched as described herein. This may furtherenhance the UWB signal transmission/reception and therefore thereliability and operation of the monitor. If impedance matching asdescribed herein is not performed, a substantial amount of energy may belost between the UWB antenna and the boundary of the infant's body (asmuch as 85-90%), resulting in a substantial decrease in efficiency and aloss of reflected energy from internal anatomic structures, makingextraction of desired physiological data more difficult, less accurateand less reliable.

In general, a plurality of UWB transmitter, receivers and/ortransceivers may be used. These elements may be multiplexed or used aspart of a phased array. Examples of arrangements of phased arrays of UWBantenna are illustrated in US 2003/0090407 (specific to the use of sucharrays for imaging).

In some variations the recumbent surface (e.g., bottom of the bassinetonto which the infant is directly placed) is flush with the outersurface of the one or more UWB antenna (transmitter, receiver and/ortransceiver), even without an intermediate impedance transformer pad,such as those described below. In such cases the outer surface of theantenna is specifically configured (1) so that the infant may be placeddirectly atop it without discomfort or risk of damage to the infant orthe antenna (e.g., it may be formed of a soft or resilient material),and the antenna itself may be adapted to have a dielectric valueapproximating the dielectric value of the infant's body (e.g.,approximately 50).

One advantage of operating a UWB sensor(s) in an isolation bassinette isthat the structure of the bassinet is physically bounded on all sides.The bassinet represents a constrained volume, and thus there is a finiterange where the target—the infant, can be located in the bassinette. Thesystem may be calibrated during installation or prior to placement ofthe infant in the bassinette to optimize the radar range andcharacterize the empty bassinette. This calibration data could then beused to create a filter that represents the empty bassinette. Once theinfant is placed in the bassinette the filter would operate on the radarreturns, producing an optimized signal that enhances the presence andmotion of the infant, minimizing the potential for detection of falsepositives.

Impedance Transformer Pad with Integrated UWB Sensor

Any of the systems described herein may include a recumbent surface withintegrated UWB components that is configured to match and/or optimizethe impedances between the UWB antenna and the infant, and therebysubstantially reduce reflection loss. In general, the recumbent surfacemay be a pad, table, platform, mattress, cushion, blanket, or the like,on which the infant is configured to lie, sit, or recline, where therecumbent surface acts as an interface between the UWB antenna and alsoacts as an impedance transformer to minimize reflection and improveenergy transfer between the antenna and the infant.

For example, the sleeping pad in a NICU bassinette may be adapted to be(or include) an impedance transformer pad coupled to the UWB antenna(s)for monitoring the infant. NICU bassinette pads are typically made ofhigh density foam rubber with a vinyl coating and are primarily designedfor comfort. Such foamed pads are typically very lossy, at least in partbecause of the presence of air pockets within the foamed material, sothat if the foam pad were placed between a UWB antenna and the infant,much of the UWB energy applied would be lost in reflection orscattering. An impedance transformer pad may be configured to avoid theloss of reflection while maintaining comfort. In addition to providing acomfortable surface, the pad could be optimized to work with the UWBmedical radar to optimize the energy transfer between the radar and theinfant, which may be particularly important given the small size of theanatomical targets in the infant. Thus, the composition of the pad andthe thickness of the pad between the radar antenna(s) and the surface ofthe pad may be configured to act as an impedance transformer. The UWBsensor(s), including transmitters, receivers and/or transceivers, may beintegrated into an impedance transformer pad, and the impedancetransformer pad may be placed beneath the infant, including on top of anexisting bassinet pad/mattress or in place of such a pad.

The impedance transformer surfaces described herein may be referred toherein as impedance transformer pads or, for convenience as simply“pads”, although any appropriate surface (not limited to a mattress-typepad), may be used. Such alternative embodiments, including blankets,pillows, seats, seat covers, garment, mattress covers, etc. configuredas impedance transformers may also be referred to as impedancetransformer pads, impedance matching pads, impedance transformers, orthey may be referred to impedance transformer structures, where thestructure refers to the form of the embodiment, e.g., blanket, pillow,seat, etc.

An impedance transformer pad may be used to efficiently transfer energyfrom one medium to another (e.g., the antenna to the infant) byminimizing reflections of the UWB energy due to impedance mismatchbetween the two mediums. In general, for non-conductive, non-magneticmaterials, the relative dielectric constant of the two mediums (e.g.,between the antenna and the subject) is the parameter of interest forthis purpose.

In general, an impedance transformer pad may be formed of one or morematerials (layers) interposed between the outer surface (antennasurface) of the UWB antenna and the outer surface (recumbent surface) ofthe pad onto which the patient will rest. These impedance transformerlayers of the pad are chosen to efficiently convey UWB energy in apredetermined bandwidth between the antenna surface and the recumbentsurface by controlling the thickness and the dielectric properties ofthe transformer layer(s).

In theory, a simple single layer impedance transformer may be fabricatedfrom a material with a dielectric value that is the geometric mean ofthe two primary mediums on either side of the transformer (e.g., theantenna and the infant), and have a thickness that is an odd multiple ofthe fundamental wavelength of the energy. Impedance transformer pads ofincreasing complexity may also be used, in which the pad includemultiple layers of material having different dielectric constants andspecific thicknesses, as described in greater detail below.

Although a more exact determination of the thickness and dielectriccomposition of the impedance layer(s) of the impedance transformer padmay be calculated as taught herein and described in greater detailbelow, in some variations impedance transformer pads having one or morelayers may be generally described as having an impedance transformerregion (e.g., the region between the transmitting/receiving surface ofan antenna and the recumbent surface) with a thickness between 0.4 cmand 7 cm (e.g., 0.5 cm to 5 cm, or in some variations 0.5 to 7 cm),where at least one planar layer of this impedance transformer region hasa dielectric between about 5 and about 20. For example, based on thetheoretical calculations and considerations described below, a typicalimpedance transformer pad may include an impedance transformer regionformed of one or more (planar) layers of a homogenous material; thethickness of the impedance transformer region, between the outer surfaceof the pad (e.g., the surface contacting the infant) and theemitting/receiving surface of the antenna is typically within the rangeof about 0.4 cm to about 7 cm, and at least one layer of material inthis region has a dielectric constant between about 5 and about 20.

Such general impedance transformer pads (having thicknesses anddielectric properties in the ranges described above) may sufficientlyminimize reflection loss of the UWB signals between the UWB antenna(s)and the infant's body to substantially increase the efficiency of energytransferred between the two, and thereby the increasing the energyreflected from internal structures within the patient, increasing thestrength of the received signal and the accuracy of the system. Inoperation, the impedance transformer pads described herein may reduceone-way reflective losses between the antenna and the subject to lessthan 50%.

In the context of the monitors described herein, the primary mediums inthe NICU bassinet are the radar antennas and the infant; thus, thetransformer material may be selected to have a relative dielectricconstant that is the geometric mean of these two mediums. The impedancetransformer pads may therefore be configured so that the thickness ofthe pad is controlled and matched to the fundamental wavelength(s) ofthe energy of the UWB sensor system, and the material composition of theimpedance transformer pad may be controlled so that the materials chosenhave a dielectric value that is within a range (e.g., the geometric meanof the antenna and the infant) of optimal values.

An impedance transformer pad may be configured to have a thicknesswithin an optimal range based on the antenna dielectric (assuming anaverage patient dielectric) and the bandwidth of the UWB signal, and adielectric (or multiple dielectrics in the case of layered pads) withinan optimal range also based on the antenna properties and the bandwidthof the UWB signal. The optimal ranges of the thickness and dielectric(s)may be determined by calculation based on the principles described ingreater detail below. In addition, the impedance transformer pads mayalso include one or more integrated UWB antenna for transmitting and/orreceiving the UWB probe signals. Such components may be integrated onthe back (e.g., non-patient contacting) side of the impedancetransformer region of the pad, and/or integrated within the impedancetransformer pads. For example, a pad may include one or more backinglayers in which the antenna(s) are embedded beneath the impedancetransformer region. In the discussion below, the impedance transformerregion refers to the region of the pad between the outer (emittingand/or receiving) surface of the antenna(s) and the outer surface of thepad on which an infant may lie (recumbent surface).

As mentioned, the optimal thickness of the impedance transformer regionof the pad may depend on the bandwidth of the UWB signal applied by thesystem and the dielectric properties of the impedance transformer regionof the pad. The dielectric(s) of the impedance transformer region of thepad may depend on the dielectric values of the antenna and of thepatient, and in the case of impedance transformer regions havingmultiple layers, the dielectric values of each layer may also be basedon the dielectric values of the other layers of the impedancetransformer region.

FIG. 3A shows one variation of an impedance transformer pad 303including an impedance transformer region 305 formed of a single layer.Beneath the impedance transformer layer is at least one UWB antenna(s)307. The UWB antenna(s) may be planar antenna and may be configured asemitters, receivers and/or transceivers. The UWB antenna is coupled(e.g., via a cable 308) to a processor 309 which may form part of theUWB monitor system. The system may include the pad, antenna(s), andprocessor. The processor may analyze and/or output sensing data based onthe UWB signals from the antenna. Additional UWB electronics may also beincluded. For example, of the systems and devices described herein mayalso include UWB electronics that are separate from or incorporated intoa processor. These UWB electronics generally are configured togenerating a UWB signal for transmission, and to aid in processing UWBsignals (reflected signals) received the by the UWB antenna(s). UWBelectronics may include signal generators, D/A and A/D converters,timing circuitry, comparators, amplifiers, filters, and the like. Forexample see U.S. Pat. No. 7,725,150, U.S. patent application Ser. No.12/765,680, published as US 2010/0274145A1, and U.S. patent applicationSer. No. 12/749,861, published as US 2011/0060215A1. UWB electronics maybe configured to generate the UWB signal(s) for emitting from theantenna(s) and processing the received signal (reflections) to extractphysiological data.

In FIG. 3A, the pad also includes a backing region 311 which may alsoact as a substrate on which the antenna(s) and impedance transformersurface sits. The backing region may be a foamed material, or any otherappropriate material, and may have dielectric that is mismatched withthe dielectric of the impedance transformer surface above it. In FIG.3A, the impedance transformer surface may have a thickness in the rangeof between about 0.4 cm and 7 cm (e.g., 0.5 cm to 5 cm, or in somevariations 0.5 to 7 cm). This impedance transformer surface is formed ofa homogenous material having a dielectric generally between 5 and 20. Insome variations this impedance transformer surface is made from asolution of silicone that has been adjusted to have the desireddielectric value by adding additives (e.g., salts, etc.). In thisexample, the outer impedance transformer layer is laminated directly onto the backing layer and antenna(s). For comfort, the pad may providesupport, yet not be excessively hard/rigid, in order to avoid creatingsores at pressure points on the body. The pad may also be easy to clean,non-toxic, hypoallergenic, and water proof Thus, in some variations theouter impedance transforming region of the pad may be fabricated fromsilicone gels. As mentioned, these gels may be doped with commonmaterials, e.g. carbon black or barium titanate, to create layers withdielectrics within the desired range (e.g., <30).

The overall shape of the pad, including the number and orientation ofthe UWB antennas, may be varied. FIG. 3B illustrates one variation of aUWB transformer pad for use with a UWB monitoring system that has fourantenna arranged across a midline region of the pad. FIG. 3B shows a topview looking down on the outer surface of the impedance transformerregion; the antenna 307, 307′, 307″, 307′″ beneath this region areindicated by the dashed boxes. In some variations the pad may alsoinclude markings indicating the preferred positioning for a patient(e.g., infant) lying on the pad. In FIG. 3B this is illustrated by theshaded outline of the infant 321. This may be indicated on the padvisually, or the pad may simply mark (e.g., in color and/or text) thelocation of the antennas and/or the desired orientation of the patient.The pad may be any appropriate size. For example, the pad may be a onefoot by one foot square, or it may be smaller or larger. The type andsize of the UWB antenna may also be adjusted; in this example, theantennas are 2 inches long.

The range of values for the thickness and dielectric of the impedancetransformer region provided above for the example shown in FIGS. 3A and3B are general, however more precise values may be calculated given theproperties of the antenna and assuming a bandwidth of the UWB signal.For example, in one variation of an impedance transformer pad having asingle layer impedance transformer region of the pad, the thickness ofthe transmissive layer of the pad will typically be centered aroundabout ¼ of the center frequency (e.g., the geometric mean of thebandwidth) of the applied UWB signals. A range of thicknesses maytherefore be determined as optimal or appropriate from this estimate. Toapproximate these values, the following assumptions are made: (1) thedesired transmission bandwidth is approximately 3 GHz to 6 GHz; (2) thecharacteristic impedance of the antenna is approximately 377 Ohm (air),and the relative dielectric constant is 1; (3) we assume that thepatient's relative dielectric constant is approximately 50 (which isparticularly accurate for bodies having a low fat content, such aspreemies).

Assuming the bandwidth of the UWB signal is approximately 3-6 GHz, thegeometric mean is approximately 4.25 GHz, which may be referred to asthe center frequency (f_(c)). In this single layer example, anapproximate optimized dielectric for the single layer may be based onthe mean value between the dielectric of the antenna and the target(e.g., the aggregate dielectric of the infant's body). For example: fora single layer quarter wavelength pad, the relative dielectric constantof pad is the geometric mean of the dielectric of air (∈_(air)) and ofthe patient (∈_(patient)) or approximately 7.07 (∈_(d)). The thicknessof the pad for the quarter-wavelength case is therefore equal to onequarter of the wavelength at the center frequency in the dielectric, or:

${{thickness}\mspace{14mu} {of}\mspace{14mu} {pad}} = {{{\lambda/4}\mspace{14mu} {in}\mspace{14mu} {the}\mspace{14mu} {dielectric}} = {\frac{c}{4\; f_{c}\sqrt{ɛ_{d\;}}} = {\frac{3\; e\; 10\mspace{14mu} {cm}\text{/}s}{4 \times 4.24\; e\; 9\; {c/s} \times \sqrt{7.07}} = {0.67\mspace{14mu} {cm}}}}}$

(where c is the speed of light, f_(c) is the center frequency and ∈_(d)is the dielectric of the impedance transformer region of the pad).

Thus, in this example, a pad such as the one shown in FIGS. 3A and 3Bmay be made using readily commercially available air antennas (∈_(air))for a bandwidth of 3-6 GHz, and therefore has a thickness of the outerimpedance transformer region of approximately 0.67 cm (e.g. between 0.6and 0.9 cm) and a dielectric value for this region of approximately 7.07(e.g., between 5 and 9). This outer impedance transformer region may beformed of silicone that is doped with carbon black to achieve thisimpedance value. The pad may also include a backing region formed offoam rubber, and a plurality (e.g. 2, 3, 4, 5, 6, 7, 8, etc.) of antennaabutting the impedance transformer region so that UWB energy is directedtoward the patient through the impedance transformer region. A systemincluding such a pad may include the pad as described above (or in anyof the other variations described herein) and a processor and/oradditional UWB electronics communicating with the antennas in the pad;in some variations an output (e.g., one or more of audible outputs,visual outputs, electronic outputs, etc.) may also be part of thesystems. The processor may include a housing, and one or more inputs(e.g., touch screens, keypads, etc.) for receiving information. In somevariations the antenna may be directly coupled to UWB electronics forgenerating the UWB signal and/or processing the received signalreflections and extracting physiological data. For example the antennamay be integrated with some or all of the UWB electronics, or it may beconnected to them, and the UWB electronics (and/or additional processor)may be positioned separately from the pad, as illustrated in FIG. 3A.

The presumed dielectric constant for the patient is based on areasonable value for preemies. Because premature infants do not have asmuch body fat, their aggregate relative dielectric constant isapproximately 40 to 60. As described above, based on this range ofvalues, a single layer quarter wavelength transformer pad may be formedat least in part of a material that has a relative dielectric constantbetween about 5 and about 20 to efficiently couple energy from theantennas to the patient. The antenna used for the pads described hereinmay have a different dielectric value (e.g., other than air) and may beoptimized to couple energy from the circuitry to a medium other thanair, which may also reduce the physical size of the antenna. Thus, basedon the antenna variation, optimal values for the dielectric constant ofthe impedance transformer pads could be somewhat lower or higher, andmay be within the range, for example, of about 5 to about 25.

A single layer quarter wavelength impedance transformer pad may beparticularly useful with narrowband signals, though its performance maydegrade as the bandwidth of the signal increases, as is the case withUWB radar. To compensate for this, multilayer transformers pads may beused, and may be better suited to minimize reflections across thedesired portion of the spectrum. Exemplary multilayer transformers padsmay include a 2 layer “quarter-quarter” transformer pad and a 3 layer“quarter-half-quarter” transformer pad, where the quarter and halfreferences are with respect to the estimated wavelength of the centerfrequency of the UWB monitor. Pads having more than three layers for theimpedance transformer region are also contemplated.

For example, three exemplary variations of impedance transformer padsare: quarter, quarter-quarter, and quarter-half-quarter variations. Thequarter-quarter is variation may provide improved bandwidth and can befabricated from materials with dielectrics between those of thecharacteristic impedance of the antennas and the dielectric of thepatient. The quarter-half-quarter may use a material for the half layerthat has a dielectric significantly above either of the other two(quarter layers) for an improvement in bandwidth over the quarter andquarter-quarter layer variations. Numerous other topologies, includingmore than three layers, are possible. Typically, however, the greaterthe number of layers, the larger associated materials cost andmanufacturing complexity; additional layers may, however, provide amodest improvement in performance.

As an example, a three layer transformer (“quarter-half-quarter”transformer pad) may provide good performance over a 100% bandwidthcase, e.g. 3 GHz to 6 GHz. Similarly, other transformer pad structures,including multiple layers, can be employed to enhance energy transfer.

FIG. 5 illustrates one variations of an impedance transformer pad thathas an impedance transformer region formed of three layers; a¼wavelength layer, a ½ wavelength layer, and ¼wavelength layer. Byhaving multiple layers, it may be possible to expand the bandwidth overwhich the transformer pad effectively moves energy. Each layer isdesignated by the fraction of the center frequency (f_(c)), e.g.,¼wavelength, ½ wavelength, etc. as a function of the dielectric of thelayer.

In FIG. 5, a UWB system includes an impedance transforming pad havingthree layers: a quarter (¼ wavelength) layer 501, a half (½ wavelength)layer 503, and another quarter (¼ wavelength) layer 504. Thus, thisvariation may be referred to as a quarter-half-quarter wavelengthimpedance transformer pad, and includes at least one integrated UWBantenna 505. As illustrated in FIG. 2, the antenna may be a UWB planarantenna 505, and may communicate with a UWB processor 509 (e.g., via RFcable 507 or other means, including wirelessly). As mentioned above,additional UWB electronics for generating the UWB signal(s) fortransmission, receiving the UWB signal reflections, and for processingthe reflections to extract the desired physiological data may beincluded as part of the processor, or separately. Further these featuresmay be integrated with the antenna or separate from the antenna andconnected as mentioned above.

In general, pads of this variation may also fall into the same range ofvalues for the thickness and dielectric values of the impedancetransformer region described generally above, however each layer mayhave its own characteristic dielectric value, and specific thickness.The overall thickness may typically be between 0.4 cm and 7 cm (theaggregate thickness of all layers of the impedance transformer region),and at least one layer of the impedance transformer region may have adielectric value between about 5 and about 20.

For example, one variation of an impedance transformer pad having athree layer quarter-half-quarter impedance transformer region may beformed so that each layer has the following dielectric and thicknessvalues, which may be estimated. Referring to the arrangement of FIG. 5and making the same assumptions mentioned above (e.g., an antenna havinga ∈_(air) of 1, a bandwidth of 3-6 GHz and a patient having a ∈_(body)of 50), the values may be calculated as illustrated below.

The half wavelength layer (layer 2) 503 may be formed of a material thatis selected for cost and/or ease of manufacturing. In this example,assume that the dielectric (∈_(d2)) is 5. Other materials, having otherdielectric values (ranging from 1 to >50) may be used. Based on thisvalue, the thickness may be calculated as:

${{Thickness}\mspace{14mu} {of}\mspace{14mu} {layer}\mspace{14mu} 2} = {{{\lambda/2}\mspace{14mu} {in}\mspace{14mu} {the}\mspace{14mu} {dielectric}} = {\frac{c}{2\; f_{c}\sqrt{ɛ_{d\; 2}}} = {\frac{3\; e\; 10\mspace{14mu} {cm}\text{/}s}{2 \times 4.24\; e\; 9\; {c/s} \times \sqrt{5}} = {1.58\mspace{14mu} {cm}}}}}$

Similarly layer 3, which is the layer of the impedance transformerregion closes to the antenna has a relative dielectric constant that isthe geometric mean of air and layer 2, or approximately 2.24 (e.g., thesquare root of ∈_(air) and ∈_(d2)). Based on this dielectric, thethickness of this layer is:

${{Thickness}\mspace{14mu} {of}\mspace{14mu} {layer}\mspace{14mu} 3} = {{{\lambda/4}\mspace{14mu} {in}\mspace{14mu} {the}\mspace{14mu} {dielectric}} = {\frac{c}{4\; f_{c}\sqrt{ɛ_{d\; 3}}} = {\frac{3\; e\; 10\mspace{14mu} {cm}\text{/}s}{4 \times 4.24\; e\; 9\; {c/s} \times \sqrt{2.24}} = {2.64\mspace{14mu} {cm}}}}}$

Layer 1 is the remaining layer closest to the outer surface of theimpedance transformer region, closest to the recumbent surface. Therelative dielectric constant of layer 1 (∈_(d1)) is a function ofdielectrics of the antennas, layer 3, and patient. It can be calculatedusing the equation:

$\sqrt{\frac{ɛ_{3}^{2}*ɛ_{body}}{ɛ_{a}}}$

where:

-   -   ∈_(a)=relative dielectric constant associated with the        antenna(s),    -   ∈₃=relative dielectric constant of layer 3, and    -   ∈_(body)=relative dielectric constant of patient's body        Thus, the relative dielectric constant of layer

$1 = {\sqrt{\frac{ɛ_{3}^{2}*ɛ_{body}}{ɛ_{a}}} = {\sqrt{\frac{2.24^{2}*50}{1}} = {15.84.}}}$

based on this dielectric, the thickness of layer 1 can be calculated asdescribed above as:

${{Thickness}\mspace{14mu} {of}\mspace{14mu} {layer}\mspace{14mu} 1} = {{{\lambda/4}\mspace{11mu} {in}\mspace{14mu} {the}\mspace{14mu} {dielectric}} = {\frac{c}{4\; f_{c}\sqrt{ɛ_{d\; 1}}} = {\frac{3\; e\; 10\mspace{14mu} {cm}\text{/}s}{4 \times 4.24\; e\; 9\; {c/s} \times \sqrt{15.84}} = {0.44\mspace{14mu} {cm}}}}}$

Thus, the thickness of the impedance transformer region is the aggregatethickness of all three layers (0.44 cm+1.58 cm+2.64 cm), 4.66 cm, andthe dielectric constants are: 15.84, 2.24 and 5. Pads such as thoseillustrated above having three layers (e.g., configured asQuarter-Half-Quarter pads) may be particularly useful, as the bandwidthmay be better than single or double layer variations.

FIGS. 4A and 4B illustrate a double-layer variation of an impedancetransformer pad of a UWB system, configured as a quarter-quartertransformer pad. In this example, the pad includes an impedancetransformer region 405 formed of a first layer 403 and a second layer401. In this example, the antennas 407, 407′ abut the second layer 401,and includes signal handling components 409, 409′, which may includeon-board circuitry (e.g., signal processing) and/or communicationscircuitry for passing the signal to other portions of the UWB system409, which may include an off-pad processor and/or UWB electronics. Insome variations, the processor and any additional UWB electronics may beintegrated into the pad.

FIG. 4B shows a top view of another variation of an impedancetransformer pad 400, similar to the variation shown in FIG. 3B. In thisexample, the positions of two antenna are indicated by the dashed boxes404, 407′ beneath the outer surface of the pad. As mentioned, anyappropriate number and positioning of antennas allowing the UWB signalto reach an infant lying on the pad may be used. Antennas which may beused as part of an impedance transformer pad include planar structures(antenna), which may minimize discomfort and are typically designed tocouple energy from the electronic circuitry to air.

In any of the variations of the impedance transformer pad havingimpedance transformer regions formed of multiple layers, the variouslayers may be laminated together. Thus, for example, single, double,triple, or more layers may be used, as indicated. In addition, one ormore additional backing layers (e.g., foam backing layers) may belaminated or otherwise affixed to the impedance transformer region.

In all of the variations illustrated above, the impedance transformerregion is formed as a planar layer extending across the entire surfaceof the pad. In some variations the impedance transformer region extendsonly over a sub-region of the surface of the pad, which may be limitedto just the region above the antenna and between the antennatransmission/receiving surface and the upper (recumbent) surface of thepad. In some variations the impedance transformer region may be slightlylarger than the underlying antenna surface. Multiple such impedancetransformer regions (“islands”) may extend across the surface of the padover top of each antenna; these discrete impedance transformer regionsmaybe surrounded by the same support layer material (e.g., foam rubber,etc.) as beneath the impedance transformer region. Such variations maybe particularly useful where multiple types of antennas having differentproperties (e.g., different dielectrics) are used. In this variation,the different impedance transformer regions may have a different numberof layers or may have different characteristic thicknesses and/ordielectrics.

Returning now to FIG. 2, another variation of an impedance transformerpad configured as a quarter-quarter impedance transformer pad with anintegrated UWB antenna is illustrated. In this example, the impedancetransformer pad includes two layers (first layer 201 and a second layer202) and an integrated planar UWB antenna 205 which is attached to theunderside of the impedance transformer pad. The UWB antenna is shownconnected via RF cable 207 to a UWB processor 209, which may be locatedoutside of the bassinet. Additional UWB electronics (not shown) may alsobe included (as part of or in addition to the UWB processer) forgenerating the signal(s), conditioning the received signal(s) and/orextracting information from the received signal(s). Alternatively, insome variations, the processor 209 and other UWB components (e.g.,electronics) may be located within the bassinet or may be coupledwirelessly to the antenna 205. In some variations, the processorcontrols the transmission and reception of UWB signals and may providedsignal processing and analysis of the patient's (e.g., infant's) vitals.Outputs, including alarms, storage of signals (including alarms, etc.),and transmission of data from the UWB system may also be coordinated andcontrolled by the processor.

The impedance transformer pads described herein may address problems andinefficiencies present in other UWB senor systems, particularly thoseused for recumbent patients. As mentioned above, “mattress” UWB sensorsfor monitoring the health of an individual in a bed or chair have beendescribed, but have not been optimized to improve radar performance.Optimization would not be possible when UWB systems are used withstandard mattress materials. For example, foam rubbers used in mostmattresses are made from styrene-butadiene or polyurethane, which haverelative dielectric constants in the range of 2 to 4 prior to beingconverted into foam, outside of the optimal dielectric range. To createfoam rubber, the base rubber compounds have gas injected into themduring manufacturing to decrease hardness and improve comfort as well asincrease insulating properties, and the introduction of gas reduces thedielectric constant of these materials proportionally to the percentageof gas by volume used in the product. Also, gas bubbles causescattering, reducing the performance of the radar. Both the miss-matchof the extremely low relative dielectric constants and scattering by gasbubbles make traditional foam rubber mattress materials unsuitable foruse in an impedance transformer as described herein. Further, thethicknesses of mattresses are much larger than the range of thicknessesdescribed herein for optimal configuration of an impedance transformerpad.

Signal Processing

Data from the UWB medical radar system may be processed to provideappropriate outputs, including cardiac wall motion waveforms orindicators, cardiac rate waveforms or indicators, and respiratorywaveforms or indicators as well as refined data derived from these basicdata types. Programmable alarms may be set by caregivers to alert themof changes to the infant's condition. The resulting data could bedisplayed on a local monitor or a centralized monitor. With connectionto the hospital network, the data could be accessed by healthcareprofessionals remotely.

In addition to detection of basic vital signs, including cardiac andrespiratory activity, the UWB sensor systems described herein may beprogrammed to detect other motions, including heads turns or limbmovement, and could be configured so that the absence of age-appropriatemotion over a pre-defined period of time triggers alarms, promptingcaregivers to check on the infant. For example, in some variation theprocessor may receive one or more inputs that may help it to monitor theinfant. For example, the processor may receive the infant's age and usethis information to appropriate toggle alerts or analysis information.For example, the amount of motion typically observed in pre-maturebabies is a function of gestational age at the time of birth. Forexample, a baby born at 28 weeks or less does not move much, with motionlimited to first clinches or limb flexes. Between 29 and 32 weeks ofgestation, motion is jerky and can include head turns. At 35 weeks, thebaby is capable of a variety of motions, including tucking into thefetal position. In addition, other sensors, such as temperature (e.g.,infrared) sensors, pressure sensors, or the like, could be integrated toprovide enhanced monitoring capabilities.

In general, the UWB signals generated and proceed to determine vitalproperties (e.g., heart rate, body movements, and the like) may behandled as previously described, for example, in U.S. Pat. No.7,725,150, U.S. patent application Ser. No. 12/765,680, published as US2010/0274145A1, and U.S. patent application Ser. No. 12/749,861,published as US 2011/0060215A1.

The system may further be configured to integrate with one or more otherhospital monitors, records, or hospital control systems. Thus, thesemonitors may interface with existing infant monitoring systems. Forexample, the processor may allow communication/interface with othermonitoring or hospital patient care systems.

In addition, the systems and devices described herein may includeautomatic on/off or other power management functions, which may also beused to toggle alerts and data collection. For example, the UWBsensors/impedance transformer pads described herein may determine whenthe patient (e.g., infant) is laying on the recumbent surface (e.g.,impedance transformer pad). Since these devices efficiently transferenergy between the UWB antenna and patient, the voltage standing waveratio (VSWR) will reflect when the patient is not present on the pad.This is relatively simple to detect in the sensor and can be used as away to tell when a patient is present, allowing the radar to go into a“sleep” mode when the patient is gone. In sleep mode, the radar mayoccasionally “wake up” to test for the presence of the patient and whendetected, resume full operation. The system may also be set up totrigger an alarm if the VSWR ratio indicates that the patient has movedoff of the impedance transformer pad.

In general, the impedance transformer pads described herein may beadapted for comfort, as the infant may be placed directly on them.Furthermore, these pads may be well adapted for use as a sleepingsurface, and particularly for an infant sleeping surface. For example,the impedance transformer pads may be flexible, pliable, soft, and/orresilient. The pad may be configured to be easily removed (and maytherefore contain coupling/uncoupling features whereby the integratedUWB antenna components in the impedance transformer pads may beuncoupled and reconnected to the rest of the UWB monitoring system(including one or more processors, displays, etc.). The impedancetransformer pads may also be configured so that it can be easily andsafely washed or laundered and/or sterilized. Thus, the impedancetransformer pad may include a waterproof or water resistant outercoating, and the antenna components may be protected from corrosion ordegradation by washing, or by contamination from blood, urine, or thelike.

Any of the impedance transformer pads described above may also includeone or more indicators, including markings, illuminated regions (e.g.,LEDs, etc.) indicating the optimal placement or positioning of thesubject on the pad, and/or the orientation of the pad on or relative tothe bassinet, bed, seat, etc. For example, the impedance transformer padmay include a color-coated or otherwise labeled region indicating howthe infant is to be oriented when laying on the pad, such as where tooptimally position the head and torso.

Although the variations of the UWB monitoring systems described aboveare illustrated in the context of infant/NICU embodiments, these systemsand devices may be used and/or adapted for use by non-infant (includingadult or veterinarian) use. For example, a impedance transformer pad maybe used on top of an adult-sized mattress for use with one or more adultpatients, including gerontological or hospital use.

Other variations of the devices and systems described herein include, inparticular, garments, seats, and/or blankets configured as impedancetransformer pads for use with UWB monitoring systems. Such impedancetransformer pads may be configured with integrated antennas and theappropriate thickness and dielectric properties. For example, animpedance transformer pads may be configured as part of car seat thatmay be used over an existing car seat and may optimally provide feedbackto a mobile UWB monitoring systems. In other variations, a blanket orbedcovering may be configured as an impedance transformer pad, which maybe applied over a patient, or beneath them as a mattress pad or thelike.

In particular, variations of the systems described here may be used forhome (rather than just NICU) monitoring. For example, parents,particularly those of infants with medical problems, are often concernedabout the undetected onset of emergent medical problems when their childis asleep. It may therefore be desirable to use the devices describedherein for active baby monitoring. Currently available baby monitorsinclude traditional audio and video monitors as well as crib pads withmotion sensors capable of detecting motion and respiration. The systemsdescribed above could be used to provide a monitoring able to detectcardiac activity and other vital signs, including gross body motion.Simplified variations of the system may be adapted for home use,including systems limited to one or two radar components, such as asingle transceiver, a separate transmitter and receiver, or twotransceivers. These systems may include an impedance transformer pad asdescribed above, or may be configured to mount or hang from the child'scrib. A communications link may be used to transmit infant data to asmall receiving station that the parents could carry with them or placenearby.

While the foregoing has been with reference to particular embodiments ofthe invention, it will be appreciated by those skilled in the art thatchanges in these embodiments may be made without departing from theprinciples and spirit of the invention, the scope of which is defined bythe appended claims. The intention(s) described herein are intended tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope and spirit of the invention.Accordingly, the protection sought herein is as set forth in the claimsbelow.

What is claimed is:
 1. A method of monitoring an infant using an ultrawideband (UWB) radar system including an impedance transformer pad, themethod comprising: placing the infant atop the impedance transformer padhaving a plurality of adjacent planar layers wherein each layer has adielectric, and wherein the thickness of each layer is approximately onequarter or one half of the wavelength of the center frequency of thebandwidth in the dielectric of that layer; and emitting a UWB signalfrom a UWB antenna beneath the impedance transformer pad, wherein thesignal passes from the antenna, through an impedance transformer regionof the impedance transformer pad and into the infant, further whereinthe impedance transformer region is arranged so that the dielectricconstants of the adjacent planar layers increase towards the infant andare between about 5 and about 20, wherein the impedance transformer padreduces the impedance miss-match between the antenna and the infant toreduce reflective loss of energy from the signal.
 2. The method of claim1, further comprising receiving a reflected UWB signal from the infantusing the UWB antenna.
 3. The method of claim 1, wherein emitting theUWB signal comprises passing the signal through the impedancetransformer region wherein the impedance transformer region has a singlehomogenous planar layer having a dielectric that is the geometric meanof the dielectric of the antenna and the dielectric of the infant. 4.The method of claim 1, wherein emitting the UWB signal comprises passingthe signal through the impedance transformer region wherein theimpedance transformer region has a thickness between about 0.4 cm andabout 7 cm.
 5. The method of claim 1, wherein placing comprises placingthe infant atop the impedance transformer pad within an NICU bassinet.6. The method of claim 1, wherein emitting comprises emitting the UWBsignal from the antenna to the infant through the impedance transformerregion without passing thought the air.
 7. A method of monitoring aninfant using an ultra wideband (UWB) radar system including an impedancetransformer pad, the method comprising: placing the infant atop theimpedance transformer pad having a plurality of adjacent planar layerswherein each layer has a dielectric; and emitting a UWB signal from aUWB antenna beneath the impedance transformer pad, wherein the signalpasses from the antenna, through an impedance transformer region of theimpedance transformer pad and into the infant, further wherein theimpedance transformer region is arranged so that the dielectricconstants of the adjacent planar layers increase towards the infant andare between about 5 and about 20, wherein the impedance transformer padreduces the impedance miss-match between the antenna and the infant toreduce reflective loss of energy from the signal.
 8. The method of claim7, further comprising receiving a reflected UWB signal from the infantusing the UWB antenna.
 9. The method of claim 7, wherein emitting theUWB signal comprises passing the signal through the impedancetransformer region wherein the impedance transformer region has a singlehomogenous planar layer having a dielectric that is the geometric meanof the dielectric of the antenna and the dielectric of the infant. 10.The method of claim 7, wherein emitting the UWB signal comprises passingthe signal through the impedance transformer region wherein theimpedance transformer region has a thickness between about 0.4 cm andabout 7 cm.
 11. The method of claim 7, wherein placing comprises placingthe infant atop the impedance transformer pad within an NICU bassinet.12. The method of claim 7, wherein emitting comprises emitting the UWBsignal from the antenna to the infant through the impedance transformerregion without passing thought the air.
 13. A method of monitoring aninfant using an ultra wideband (UWB) radar system including an impedancetransformer pad, the method comprising: placing the infant atop theimpedance transformer pad having a plurality of adjacent planar layerswherein each layer has a dielectric, and wherein the thickness of eachlayer is approximately one quarter or one half of the wavelength of thecenter frequency of the bandwidth in the dielectric of that layer; andemitting a UWB signal from a UWB antenna beneath the impedancetransformer pad, wherein the signal passes from the antenna, through animpedance transformer region of the impedance transformer pad and intothe infant, further wherein the dielectric constants of the planarlayers are between about 5 and about 20, and wherein the impedancetransformer pad reduces the impedance miss-match between the antenna andthe infant to reduce reflective loss of energy from the signal.
 14. Themethod of claim 13, further comprising receiving a reflected UWB signalfrom the infant using the UWB antenna.
 15. The method of claim 13,wherein emitting the UWB signal comprises passing the signal through theimpedance transformer region wherein the impedance transformer regionhas a single homogenous planar layer having a dielectric that is thegeometric mean of the dielectric of the antenna and the dielectric ofthe infant.
 16. The method of claim 13, wherein emitting the UWB signalcomprises passing the signal through the impedance transformer regionwherein the impedance transformer region has a thickness between about0.4 cm and about 7 cm.
 17. The method of claim 13, wherein placingcomprises placing the infant atop the impedance transformer pad withinan NICU bassinet.
 18. The method of claim 13, wherein emitting comprisesemitting the UWB signal from the antenna to the infant through theimpedance transformer region without passing thought the air.